I'm trying to implement MCU Boot loader based on the example for the FRDM64. I see that many of the functions are not implemented except for use with UART0. I am attempting to use UART4. One function that I'm attempting to replicate for UART for is the following. I don't understand what the line that begins with SIM->SOPT5 is for and as there is nothing similar for UART4 I have no way to replicate it. Can someone tell me what this line is for and whether it's necessary to get the MCU Boot Loaders working on UART4. So far when using the BLHost command I am attempting to get property 1 and get a response that there was "No response received for ping command". Any help would be appreciated
void UART0_InitPins(void)
{
/* PORTB16 (pin 62) is configured as UART0_RX */
PORT_SetPinMux(UART0_RX_PORT, UART0_RX_PIN, kPORT_MuxAlt3);
/* PORTB17 (pin 63) is configured as UART0_TX */
PORT_SetPinMux(UART0_TX_PORT, UART0_TX_PIN, kPORT_MuxAlt3);
SIM->SOPT5 = ((SIM->SOPT5 &
/* Mask bits to zero which are setting */
(~(SIM_SOPT5_UART0TXSRC_MASK)))
/* UART 0 transmit data source select: UART0_TX pin. */
| SIM_SOPT5_UART0TXSRC(SOPT5_UART0TXSRC_UART_TX));
}